This invention relates to fluid filtering and, more particularly, to an insert for a filter cartridge and its method of construction.
One type of filter cartridge in common use employs inner and outer concentric cylindrical filter elements separated by an annular region. The cartridge is mounted in a housing having an inlet communicating with the outer surface of the outer filter element and the inner surface of the inner filter element and an outlet communicating with the annular region. Fluid flows radially inward through the outer filter element and radially outward through the inner filter element to the annular region and then flows axially through the annular region to the outlet. A problem of the described filter cartridge is the tendency of its filter elements to collapse toward the annular region due to the opposing forces exerted thereon by the inlet pressure. This tends to restrict fluid flow to the outlet and to reduce the useful life of the filter elements.
U.S. Pat. No. 3,988,244 teaches the use of a so-called fluid carrier element in the annular space between concentric filter elements in the form of a molded plastic mesh or netting wound about itself several times. The carrier element completely fills the annular region so as to function as a spacer in preventing collapse of the filter elements and permits transverse and axial fluid flow through the annular region by virtue of the openings in the mesh or netting.